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Sept. 19 (UPI) -- Further evidence shows that it's best not to double up on blood thinners by taking aspirin along with commonly prescribed warfarin and other blood thinners to lessen the risk of bleeding complications. A study by University of Michigan researchers, published Monday in JAMA Network Open, found that when aspirin use among 6,700-plus patients taking warfarin decreased by 46.6%, their risk of having bleeding complications dropped significantly: by 32.3%.
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Nationwide, about 11.5 million prescriptions were written for warfarin in 2020, making it still widely used despite the advent of several new "blood thinners."
Previously, the team of researchers had found that people with no clear cardiovascular risk who took aspirin in combination with warfarin had a higher rate of bleed complications. The new study confirmed this by actively stopping aspirin use.
And while the new study looks specifically at warfarin, "We've previously looked at other blood thinners and found the same results," Dr. Geoffrey Barnes, the study's senior author, told UPI in a phone interview.
"While this study focuses on warfarin, I think it's reasonable to apply the findings to Xarelto or Eliquis for people who are taking aspirin without a clear indication," said Barnes, a cardiologist at the University of Michigan Health Frankel Cardiovascular Center in Ann Arbor.
He is also an associate professor of internal medicine at the University of Michigan Medical School.
He added: "The main take-home point is this study shows aspirin is not a benign medicine and it's really important to talk to your doctor...because it may be that aspirin is causing more harm than good."
Barnes said the situation has arisen either because doctors have recommended aspirin on top of a blood thinner to their patients -- which shows the need for physicians to be educated on the topic -- or people have decided to take aspirin on their own because of broadly disseminated messaging that the medicine may prevent heart attacks.
He said the study's design showed that taking a systematic approach to the issue led to quick improvement.
The study's participants were treated at anticoagulation clinics across Michigan for venous thromboembolism, or blood clots, as well as atrial fibrillation, or irregular heart rhythm, that may cause stroke.
Barnes explained that it is customary for pharmacists and nurses to work in such clinics because warfarin "requires a lot of close monitoring and dosage adjustment."
Nurses looked in medical records for cases of patients treated with warfarin who also took aspirin despite not having history of heart disease. The nurses systematically notified doctors when such cases were spotted to determine whether aspirin was needed.
Before the clinic's nurses were involved, there was a slight decline in unneeded aspirin use; after the nurses became involved, the decline was "dramatic," Barnes said.
In fact, he said, one of the new study's surprising findings was just how quickly the rate of aspirin use declined, he said.
When the investigators began the study, Barnes said an effort already was underway by doctors to reduce aspirin use, "and our findings show that accelerating that reduction prevents serious bleeding complications which, in turn, can be lifesaving for patients."
The researchers cited previous studies that found concerning links between the concurrent use of aspirin and different blood thinners.
They said many of the study's participants most likely were taking aspirin for primary prevention of heart attack or stroke, now known to be less effective than once believed, and no one took them off of aspirin when they started warfarin.
This underscores the importance of only taking aspirin under a physician's direction and not to begin taking over-the-counter medicines such as aspirin with without having a clinician's input to determine whether the expected benefit outweighs the risk, the researchers said.
